Fluid lift control valve for oil wells



Feb, 13, 1951 BRYAN FLUID LIFT CONTROL VALVE FOR OIL WELLS 2Sheets-Sheet 1 Filed March 18, 1949 V INVENTOR.

A TT'O r/vm THOMAS Ben/w 3 741F342 4 w w Ar Feb. 13, 1951 BRYAN2,541,807

FLUID LIFT CONTROL VALVE FOR OIL WELLS Filed March 18, 1949 2Sheets-Sheet 2 'THaMAsE'. BRKAA/ INVENTOR.

BY & Q4

A -r fbE/VE Patented Feb. 13, 1 951 S PATENT OFFICE FLUID LIFT CONTROLVALVE FOR OIL WELLS I Thomas E. Bryan, Fort Worth, Tex.

Application March '18, 1949, Serial No. 82,215

This invention relates to devices for flowing oil wells by fluidpressures, as by inducting into such wells gas under relatively highpressures from the earths surface, and it has particular reference toespecially designed valves arranged at different levels or stages in oilwells, and involves structure generally relating to that disclosed in U.S. Letters Patent No. 2,236,864, dated April 1, 1941, assigned to ThomasBryan, and it has for its principal object the provision of a valveconstruction adapted to be disposed at predetermined spaced elevationsalong the fluid conduits of an oil well and adjusted for automaticoperation by fluid pressures of different values to intermittentlydischarge well fluids from such well.

A further object of the invention is that of providing an arrangement ofco-axial conduits by which the well fluids can be raised through onechannel while suitable gas pressures can be applied through the otherchannel from the earths surface to move the liquids flowing into thewell from the production areas thereof, the natural pressures in saidwell having been depleted and are therefore incapable of raising the oilcolumn to the earths surface.

Yet another object of the invention resides in the provision of a tubingfitting for the installa- 1 tion of the valve assembly wherein isdefined a receptacle for the latter adapted to protect the assembly fromdamage in running the tubing into and out of the well, and forming thevalve housing to especially adapt. the same for attachment in thereceptacle to insure rigidity, projecting its greater length into thereceptacle to prevent vibration and possible injury from similarfactors.

It is an important object of the invention to provide a system of flowvalves capable of installation along a tubing string which functions asa flow conduit for well fluids while the well casing, closed at thebottom from the production area of'such well by a packer, affords achannel into which gas pressures can be introduced to be admitted to theflow conduit through the said valve system in stages when, acted upon bythe gas pressures and in accordance with production capabilities of thewell in which the installation is made.

An object of the invention is that of providing an economical medium forautomatically producingoil from wells whose natural pressures areincapable of flowing the oil from such wells, and

providing a system by which relatively high pressuresjcanbe inductedinto the wells while preventing the application of excessive artificial8 Claims. (Cl. 103-233) pressures to the producing oil sands throughwhich the oil therein may be forced back into the formations, impairingthe normal production capabilities of the well.

One object of the invention resides in the provision of a valvestructure of the character described in which is embodied a closurecontrol device whereby extended pressure contact areas are afforded tooffset or nullify the effect of fluid velocities on the valve elementsand insure greater efficiency in operation. I

Broadly, the invention contemplates the provision of a valve embodyingstructural features which insures proper response to applied pressuressufficient to raise well fluids and is capable of utilizing theincreased energies in gas at higher pressures when expanded to a lowerpressure in the tubing.

While the foregoing objects are paramount, other and lesser objects willbecome manifest as the description proceeds, taken in connection withthe appended drawings wherein:

Figure 1 illustrates, in vertical section on lines li of Figure 3, avalve structure embodying the invention, showing a body adapted to theremovable or drop assembly illustrated in Figure 6.

Figure 2 is a fragmentary illustration, on lines 22 of Figure 3, showingone of the vertical grooves in the body member.

Figure 3 is a plan view of the Valve shown in Figure 1.

Figure 4 is a transverse sectional view of the valve assembly taken onlines 4-4 of Figure 1.

Figure 5 is an inverted plan view of the invention.

tion, a modified arrangement of the closure members.

Figure 10 illustrates, in side elevation, a special fitting adapted forconnection into the tubing string, and showing portions cut away toillustrate the valve installed therein.

Figure 11 is a. plan View of the fitting in Figure 10.

Figure 12 is a transverse sectional view through the fitting on lines|2--l2 of Figure 10.

shown Figure 13 is a vertical sectional view of a type of fittingemployed at the bottom of the tubing string for receiving the drop valveshown in Figure 6, and

Figure 14 is a vertical cross-sectional 'view of a well illustrating atypical installation and showing a typical time cycle device connectedtherewith.

While the embodiment of the invention is primarily a valve structure, itembraces a complete system of valves and flow conduits by which oil isproduced from wells which would otherwise require the use of pumpingequipment.

Production can thus be accomplished through a typical installation, suchas that illustrated Figure 14, in which a casing I is arranged in a wellbore H and a string of tubin or flow conduit l2 arranged co-axiallythereof. A packer I3 is installed near the lower end of the casing l0.and provides a seal about the tubing l2 defining an annular space Mtherearound inside the casing. 13-. A perforated tail pipe |5 extendsbelow the. packer i3 into theproduction area 160i the well.

The well fluid is conducted, to the earths surface, through the tubingl2 when acted upon by artificial gas pressure introduced into the space.M in the casing it], through a pressure line I! in, the casing head IS,the pressures being controlled by any. conventional type of pressureregulator. A time cycle mechanism may also be employed to introducepressures into the conduits at predetermined intervals, or as the wellfluid flows into the bore H from the producing formation it. Suitableflow pipes l9 and 253 may. be provided for conveyin the oil to storagefrom. the. head l8.

The valve structure employed in theinvention and installed in the flowline or tubing. 2 at properly spaced. intervals, is housed according tothe specific use to. which the same is placed, as will become apparentby reference to Figures 1, 2 and 6 as compared. to the structures shownin Figures 8, 9 and 10. The structure illustrated in Figure I,particularly, is especially adapted to be installed. in the removable ordrop valve assembly shown in Figure 6 which is designed for installationin a special fitting shown. in Figure 13 at the lower end of the tubing.string. l2 and just above the packer l3, as illustrated in Figure 14.This fitting may be categorically referred to hereafter as the unloadingchamber through which all well fluids are discharged from the annularspace Is. in the casing is after the packer I3 is set. After theunloading operation, the annular space It in the casin I!) being dry,oil from the producing formation H3 is flowed upwardly through. thetubing |2 to storage aided by gaseous pressures introduced into theannular space M and admitted to the tubing |2 in stages at differentelevations to raise the liquid column.

In Figure 1 the valve assembly is shown encased within a housing 2|having a body portionv 22, the housing being formed with threadedportions 23 and 24 above and below the body portion 22, while a tailportion 25 is defined below the lower threaded portion 24 of the housing2|. A central bore 26 is formed through the housing 2| and a sleeve 2'!is arranged intermediate the ends thereof and has a central port 28therethrough with seats 29 and 30 formed on each side. A stem 3| isarranged in the bore 26 and extends concentrically through the bore 28of the sleeve 21, a closure 32 being formed on the stem 3| above thesleeve 21 and adapted to engage the seat 29 thereon to close the port 28under pressures entering the inlet 33 into the upper chamber of the bore26 above the sleeve 21 therein.

A closure 3 is formed on the stem 3| below the sleeve 2'! and is adaptedto engage the seat 30 therein alternately with the closure 32 in closingthe port 23 through the sleeve. 21 The closure 34 is normally heldagainst the seat 30 by a spring 35 arranged about the lower end of thestem 3| and which will yield under pressures applied through the inlet33 previously referred to. A 'plug 36 is pressed or otherwise securedwithin the upper end of the housing 2| and functions to guide the upperend of the stem 3| which extends into a bore 3'! to properly center thestem 3| in the bore 26 and guide the closures 32 and 34 to their seats29 and 30.

The lower end of the bore 28 is interiorly threaded to receive anexteriorly threaded follower 33 which may be threaded into and outofthe, hcusing 2| against the spring 35 to increaseor. decrease thetension thereof thus con-. trolling the amount of pressure requiredthrough theinlet 3.3, to displace the closure 34, fromits seat 32. Alock-nut 3,9 is threaded upon the followertt whereby the latter issecured in, its adjusted positions. An, orifice 40 is, providedconcentrically of the follower 38. to discharge pressures from thechamber ll within the follower 38, and the bore, 25, in cooperationwith. another outlet passage hereinafter referred to.

As, apparent in Figures 2, 3, 4. and 5 the body portion 22,, is formedwith a plurality of verti.-.

cal grooves 42 which are partially enclosed bya sleeve 33 presseduponthe body. portion 22 in. a

manner shown in Figures 1, 3, 4 and 5. By this.

means the ressures entering the housing 2| through the port 33-.are,effective on the element 34 to ,closethe, valve. The stem 3|,shownindetail in. Figure 7, has a free-floating. piston45s1idablyarranged. thereon below. the closure 33 and against which the sprin3.5.exerts its tension to insurethe positive operation of thestem 3| toclose the lower seat 30 by the. closure- The valve. assembly illustratedin Figures 1, 2, 3,4 and, 5. is housed within av removable casingid-which, has upper and lower sections 41 andJIB threaded upon. theportions. 23and 24 of the housing, 3|. The upper section 4'? has arounded shoulder 4.9 at its upper end about which is arranged. aplurality of ports 53. A spear 5| is formed on the upper end of theupper section 41 by which. the assembly can be removed by a cablelnotshown), the lower section 48 being substantially fiat on the bottom andadapted to engage. a. supporting shoulder. 53v formed in the bottom. ofa fitting 54, shown. in Figure 13, by which it is adapted to beinstalled in the tubing string i2, in the manner shown in Figure 14, andwhich will presently be described indetail.

The fitting 54, illustrated in Figure 13, is swaged providing. reducedportions 55 and 56 at each end, the larger body portionor shell 54embracing a tubular sleeve 57 arranged concentrically of. the member 5 3having an interiorly threaded flange 58. formed at its lower end intowhich a tube (not shown) may be connected and which extends into thetail pipe I5. Tubular couplings 59 are arranged radially on the member5T -and extend through the walls of the body portion of the shell E iand provide communication between the sleeve 5'1? andthe annular space Mwithin the casing in. The fitting 54 is eon nected to the tubing l2 ateach of its reduced 6i of the sleeve 51 isbevelled inwardly to expe ditethe seating of the drop valve assembly thereinto.

Above and below the valve housing 2!, and the assembly illustrated inFigurefi, arearrangements of sealing rings or cups 62 and 63 arranged onthe upper and lower sections 41 and 48 of the drop valve assembly toisolate the port 33 in the annular space defined by the reduced portion84 intermediate the ends of the assembly, as shown in Figure 6, theopposing ends of the upper and lower sections AT and 48 being tightlyfitted against the collar 42 arranged about the body portion 22 of thevalve housing 2|. The couplings 59 provide communication between theannular space defined about the drop valve assembly within the member 51and the space M within the casing H].

A latch 65 is pivotally attached to the bottom of the drop valve by apin 66 which is capable of being sheared when the drop valve assembly isremoved by a wire line (not shown). The fitting 55 is installed in thetubing in the manner illustrated in Figure 14 near the packer l3. Thelatch 65 is adapted to drop into a slot which may be formed in the lowerend of the sleeve 51 and at the bottom thereof just above the shoulder53 therein upon which the drop valve assembly rests when seated. Thisarrangement will prevent the drop valve assembly from being displacedfrom its seat by pressures from the producing area it below.

In Figure is illustrated a fitting 61 which is capable of beingconnected into the tubing string l2 by suitable couplings 68, in themanner illustrated in Figure 14. The member 61 is threaded on each endand is formed with a receptacle 69, as in Figure 10, to receive a valveassembly which is illustrated fragmentarily in Figures 8 and 9.

Spaced above the receptacle 69 is an integral hood It affording furtherprotection for the valve assembly arranged in the receptacle 89.

The valve assembly shown in Figures 8 and 9 is similar to the valveillustrated in Figures 1 through 5. It will become apparent, however,that the housing 'H in this latter structure does not have the sleeve orcollar 43 thereon although its port I2 is formed inthe polygonal-head13, as illustrated in Figure 8. A port 14 is formed in the housing Hbelow the head 13 and the sleeve 15 therein and this port communicateswith a port 16 in the wall of the fitting 61 providing communicationbetween the valvehousing H and the receptacle 69 when the'assembly isinstalled in the manner illustrated) in Figure 10. The upper end of thehousing H is closed by a flanged plug ll threaded into the member H, andthe upper end of the valve stem 18, arranged through the port 19 in thesleeve 15, operates within a recess formed within the plug 11.

The valve housing II is formed with a threaded portion as just belowthe. head 13 by which the assembly is threaded into the upper end of thereceptacle 69 so that the major portion of the housing H extendsdownwardly into the receptacle 59 and is thus protected against damagefrom vibrationand other factors. on the stem 18 is a pair of closures 8|and 82 adapted to alternately engage the seats 83 and 84 in the sleevemember 75. the lower end of the stem 18 to provide sufiieient tensionagainst the lower seating member; 82 to retain the same normally againstthe seat, in

A Spring 85 is arranged about 6 the same; manner as thatof thearrangement illustrated in Figure-l.

The valve structure shown-in Figure 1 8 is=modi-= fied, as illustratedin- Figure9, whereby the seat:

ing member BI is eliminated from-the -stem-18 thelatter extendingonly-'intothe' port '19- inth'e sleeve 15, and -a ball 86 isprovidedf'orclosin'g' the port l'9, by engagingtheseat 83in theupper end of thesleeve 15; and is capable of being raised by the stem- 'l8--i-n themanner shown-in- Figure 9.

Itis a prime object of the invention to-liftthe' oil, as nearly aspossible, in accordance with normally plugged or have a system ofgate-valves thereon (not shown) and the tubing sealed;

Such a method of discharging liquids from the casing I9 is desirable toprevent forcing the oil;

through the valves installed at spacedgintervals-'- I in the tubing l2and thus avoid damage th'ereto through lodging sand, rocks, and othersubstances therein. Oil will rise from the producing area I6 into thetubing t2 and can be raised to the earths surface by continuing to applygas pres-- sures to the casing H! to be admitted to the tub-* ingthrough the valves therein;

In construction, as previously pointed out, the valve shown in Figures 8and 9 is identical in principle with the structureillustrated in Figure1, the primary difference residing in the respective housings. The lowerend of each valve structure, the tail portions 25 and H being alike,are" closed at their lower ends by followers 38 which have ports 48therein. These elements are not is shown in Figures 8 and 9.

In a typical installation the valves, are installed with the lower valveelements 82* seated, under the pressure of the springs 85,"as shown inFig ures 8 and 9. With no pressure in the casing H} or in the tubing [2such positions of the stems with their closure elements are normal. Assoon as the annular space M within the casing" ifi=has been unloaded, aspreviously described, the upper closure elements'32 and 8 Ion the stems3 tandjlty or the ball 86, will engage the seats 29 and 83' under gaspressures existing in thecasing I83 Oil rises into the tubing i 2 fromthe producing area 16 through'the tail pipe 15, and a standing valve(not shown) which may be threaded into the element 58 of the fitting 54if desiredyand submerges the valves. As the column of fluid increasesits weight will exert sufficient pressure upon the pistons and the upperclosure elements; through theparts 48 and 14, respectively, to; displace the same from their seats to admitgas pressures to the tubingandexpel the liquid there-,- from. The rapidly decreasing oil pressureswith in the tubing will enable the upper elementstobe reseated underthegas pressures exerted upon the same.

As gasenters the lower body of the valve hous ing 13 the pressuresbecome effective onthe upper face of the piston Q5 while the underside,of the latter is exposed tothe pressure of the oil column in the tubingl2 through the port 40,,

Gas escaping through the port 14, when the piston is moved downwardly,lightens the oil column permitting the piston 45 to be depressed by gaspressures entering through the ported sleeve 21 or 15 and when a properdifierential of pressures, for which the valve is set, occurs the upperseating element 8|, or ball 85, will engage the seat 83 closing thevalve against the gas pressures.

Each valve operates in this fashion until all fluid in the casing hasbeen transferred into the tubing l2 through the fitting or chamber 54whereupon the removable drop valve is installed, as previouslydescribed, the upper seating element 32 engaging the seat 29.

The well fluid may now rise into the tubing around the member 57in thechamber 54 to a level which is determined by the gas pressures in thecasing and the tension of the spring 35 whereupon the pressure of theoil column is effective through the ports 40 and 4 (or is and 74 asapplied to the other valves) below the seating elements to force theupper seating element 32 (or 8| with the aid of the spring 35, on itsseat and admit gas pressures to the tubing in the manner previouslyexplained. When a sumcient quantity of the gas pressure has been passedinto the tubing to lighten the oil column and lift the same to thesurface, the gas pressure enterin the ports 33 (Figure 1) and 72 (Figure8) will become efiective downwardly on the piston 45 to close the valveagainst the tension of the spring. The other valves above will functionin like manner, successively, as the oil, or other fluids, reaches theproper height to submerge the valves and have sufficient weight toactuate the same.

It is apparent that the piston 45, which has been described as slidableor free-floating on the stem 3|, will assume the position shown inFigures 1, 2 and 8 when the lower seating element 34 or 82 is againstits seat and in such position will close the port 44 (Figure 2) or E4(Figure 8) and close the same against oil pressure from the tubing. Thepiston 45 is relatively closely fitted in the chamber in the lowerportion of the valve body and actually functions as a piston. Thus, oilpressures from the tubing is effective only on the bottom of the piston45 while the lower element 34 or 82 is against its seat. When gaspressures in the casing reach a value suitable to overcome the backpressure of the oil in the tubing such gas pressures will be effectiveon the top of the piston to move the same downwardl relieving, to someextent, the tension of the spring 85 and opening the port 74 so thatsuch pressures will pass into the tubing to raise the liquid column.

As the port '14 is initially cracked open enough gas or casing pressurewill be admitted to the tubing to lighten the fluid column by aeration,as previously described, to permit the piston 45 to be further depressedagainst the tension of the spring 35 (Figure l) 01' 85 (Figure 8) andfree the stem so that the lower seating element can be moved furtheraway from its seat to fully open the passage 28 or 79 and, at once,fully open the port 14 (Figure 8) or the port 44 (Figure 2) and flow thewell,

It is to be understood that all of the valves have the same function andoperate in an identical manner. The elements referred to in onestructure, although having different character references, have similarfunctions. The seating elements, valve stems and, springs operate in anidentical manner.

Obviously, when the gas pressures in the casing and tubing areequalizedno fluid can reenter the casing through'any of the valves forthe reason that they remain closed, opening only when the casingpressure is greater, and under such conditions the passage of liquidstherethrough is resisted. I

Certain changes and modifications in the structure herein shown anddescribed may be resorted to from time to time by persons skilled in theart without departing from the spirit and intent of the invention or thescope of the appended claims.

What is claimed is:

1. In a flow valve for oil wells comprising a tubular housing forinstallation in a fitting in a well tubing, an inlet port in one end ofsaid housing and an outlet port in its opposite end, a pas sage betweensaid inlet and outlet ports, a seat formed on each end of said passage,a stem operating in said passage having opposing seating elements formedthereon alternately engageable with said seats, a piston element closelyfittingin said tubular housing and slidable on said stem and engagingthe lowermost of said seating elements and normally closing said outletport, a spring on said stein tensioning said piston element andyieidable to well pressures applied to said piston to open said outletport and aid in moving said stem to open said passage and close thesame.

2. In a gas flow valve for oil wells comprising tubular housing adaptedfor installation in a fiting connected in a well tubing, a gas inletport in one end of said housing and an outlet port spaced from saidinlet port in said housing, a passage between said inlet and outletports, a seat formed on each end of said passage, a valve stem operatingin said passage and having opposing seating elements formed thereonalternately engageable with said seats, a piston element slidablyoperating in the lower portion of said housing below said passage andslidable on said stem to engage one of said seating elements, the saidpiston element being normally positioned to close said outlet port, aspring on said stern engaging said piston and yieldable to gas pressureson said piston to open said outlet port and aid in moving last namedseating element to open said passage and close the same upon theoccurrence of pressure differentials between said inlet and outletports.

3. In a gas lift device for oil wells and mounting therefor, a wellcasing, a tubing in said casing, a tubular fitting connected atdifierent levels in said tubing, a valve receptacle formed on saidfitting having communication with the said tubing, a valve assemblythreadedly supported in said fitting and having a portion exposed to gaspressures in the casing, the said valve assembly comprising a housing,gas inlet and outlet ports in said housing, a passage formed axially onsaid housing between said ports and a valve seat on each end of saidpassage, a valve stem operatively arranged through said passage, a pairof seating surfaces on said stein alternately engageable with said valveseats to close said passage, a spring on said stern normally retainingone of said seating surfaces on its seat, a piston closely fitting insaid housing and slidably arranged on said stem below said passageclosing said outlet port and engaged by said spring and yieldable to gaspressures in said casing to move on said stem whereby said pressures canactuate said stem to open said outlet port and close said passage untila predetermined pressure differential occurs between said tubing andcasing to reopen said passage.

4. In a device for raising oil in an oil well having a casing and tubingtherein, a fitting connected at different levels in said tubing, a valvereceptacle formed on said fitting and having communication with saidtubing, a valve removably supported in said receptacle comprising ahousing having gas inlet and outlet ports therein, a communication insaid housing between said ports and a seat formed on each end of saidcommunication, a stem operatively arranged through said communicationand having seating elements thereon for alternately engaging said seats,a spring in said housing associated with said stem exerting tensionthereon to normally retain one of said seating elements against one ofsaid seats, and a piston member slidable on said stem and slidablyoperating in said housing below the lowermost of said seating elementsclosing said outlet port and amenable to gas pressures to compress saidspring whereby said pressures can actuate said stem to open said outletport and close said communication until a predetermined pressuredifferential occurs between said casing and tubing to reopen saidcommunication.

5. In a gas lift device for installation in an oil well, a tubing insaid well, a fitting connected in said tubing and having a valvereceptacle formed thereon and having communication with said tubing, avalve housing threadedly secured in said fitting to expose a portionthereof to gas pressures exteriorly of said tubing and having an outletport theren in said receptacle, a gas inlet port in the exposed portionof said housing, a passage formed in said housing intermediate saidinlet and outlet ports, a seat formed on each end of said passage, avalve stem operatively arranged through said passage and formed withseating surfaces alternately engageable with said seats to close saidpassage, a spring on said stem normally urging one of said seatingsurfaces to its seat, a sliding piston on said stem adjacent to one ofsaid seating surfaces and closing said outlet port and engaged by saidspring, and amenable to gas pressures to move on said stem against thetension of said spring whereby to open said outlet port and said stemcan move to open said passage and close the same at the opposite endafter a predetermined interval.

6. In a gas lift mechanism for admitting a lifting fluid to a liquidcolumn inan oil well having 2 a string of tubing and casing and a packertherein, a fitting connected in said tubing at spaced intervals andhaving a valve receptacle thereon, a valve housing having an opposingarrangement of seats and a communication between said seats installed insaid receptacle on said fitting externally thereof, a valve stemoperable through said communication and having seating elements thereonadapted to alternately engage said seats, a spring in said housingasociated with said stem capable of exerting a pressure thereon tonormally retain one of the said seating elements against one of saidseats, inlet and outlet openings in said housing for the passage of saidlifting fluid, means slidable on said stem below said seating elementsand closely fitting in said housing and engaged by said spring to closesaid outlet opening and amenable to gas pressures to compress saidspring whereby said pressures can pass 10 through said outlet openingand actuate said stem to close said communication when a pressuredifferential occurs between the casing and the tubing.

posing seats formed on the ends of said passage,

a stem operatively arranged in said housing and through said seats, apair of closure elements formed on said stem alternately engageable withsaid seats, a piston member closely fitted in said housing and slidablyarranged on said stem below the lowermost of said closure elementsclosing said outlet port and aiding in the operation of said stem,tensionedmeans on said stem engaging said piston member for normallyretaining the lowermost of said closure elements against its said seatwhereby, when gas pressure is applied to said piston member, said outletport is opened and tension on said stem is relieved and said stem canmove to open said passage and close the same from the opposite end aftera predetermined interval.

8. In a gas lift mechanism for oil wells having a casing and tubing, aplurality of fittings spaced along said tubing, each having a valvereceptacle exteriorly thereof open to said casing at one end, a valvehousing arranged in each fitting and having a portion exposed to gaspressure in said casing, a gas inlet port in said exposed portion and anoutlet port in said housing open to said fitting through saidreceptacle, a passage between said ports providing communication betweensaid ports and a seat at each end of said passage, a stem operativelyarranged through said seats and having a pair of opposing seatingsurfaces formed thereon alternately engageable with said seats to closesaid passage, a tensioned piston element closely fitting in said housingand slidably operating on said stem to normally close said outlet portand urge one of said seating surfaces to its seat and yieldable topressure in said casing whereby to open said outlet port and saidpressure can force the opposite seating surface to its said seat after apredetermined interval.

THOMAS E. BRYAN.

REFERENCES CITED The following references are of record in the fileofthis patent:

UNITED STATES PATENTS Carlisle Mar. 22, 1949

